Cylinder head for DOHC internal combustion engine with four valves per cylinder

Abstract

In a cylinder head for a DOHC internal combustion engine of the type having four valves per cylinder, a thin, flat recess is formed in the wall above an upper deck in such a way as to communicate an oil supply passage and an upper side of the upper deck. An oil return passage is provided adjacent a head bolt hole for providing communication between the recess and a lower side of a lower deck so that oil having lubricated parts and portions of the engine flows down to the upper side of the upper deck from which it is conducted to the lower side of the lower deck through the recess and the oil return passage. From the lower side of the lower deck, oil is returned to an oil pan by way of a cylinder block.

What is claimed is: 
     
       1. A cylinder head for a DOHC internal combustion engine of the type having four valves per cylinder, comprising: a combustion chamber;   two intake valve openings and two exhaust valve openings communicating with said combustion chamber:   two intake ports and two exhaust ports communicating with said intake valve openings and said exhaust valve openings, respectively;   two first supporting portions for slidably supporting two intake valves which open and close said intake valve openings:   two second supporting portions for slidably supporting two exhaust valves which open and close said exhaust valve opening;   a plurality of bearing portions for rotatably supporting thereon two camshafts for driving said intake valves and said exhaust valves, independently;   two third supporting portions for respectively supporting Y-shaped rocker arms for driving said two intake valves and said two exhaust valves, independently;   said third supporting portions being located outside of the axes of said camshafts;   a lower deck;   a plurality of head bolt disposed holes under said bearing portions, respectively and extending through said lower deck to open to the outside of said lower deck;   an upper deck;   a plurality of recesses disposed under said bearing portions and laterally outside of upper ends of said head bolt holes, respectively and communicated with an upper side of said upper deck; and   a plurality of oil return passages disposed under said bearing portions and laterally outside of and in parallel with said head bolt holes to provide communication between said recess and a lower side of said lower deck.   
     
     
       2. The cylinder head according to claim 1 wherein said upper deck is located intermediate between the upper and lower ends of the cylinder head. 
     
     
       3. The cylinder head according to claim 2 wherein said lower deck is located at the lower end of the cylinder head. 
     
     
       4. The cylinder head according to claim 3, further comprising oil supply passage means for allowing oil to flow down to the upper side of said upper deck after having lubricated parts and portions of the engine. 
     
     
       5. The cylinder head according to claim 4, further comprising a plurality of cavities under said bearing portions and a plurality of access holes formed in said bearing portions, said access holes being communicated with said head bolts holes through said cavities so that a plurality of head bolts are inserted into said head bolt holes through said access holes and said cavities. 
     
     
       6. The cylinder head according to claim 5 wherein said third supporting portions are respectively formed with adjuster installing openings for receiving therewithin lash adjusters for said Y-shaped rocker arms, said adjuster installing openings being arranged on a straight line which is equidistant from said two intake valves and said two exhaust valves. 
     
     
       7. The cylinder head according to claim 6 wherein said bearing portions comprises two bearing portions for supporting one of said camshafts for driving said intake valves and two bearing portions for supporting the other of said camshafts for driving said exhaust valves, said first mentioned two bearing portions being located outside of said first supporting portions for said intake valves and said second mentioned two bearing portions being located outside of said second supporting portions for said exhaust valves, said adjuster installing openings being equidistant from said first mentioned two bearing portions and said second mentioned bearing portions, respectively. 
     
     
       8. The cylinder head according to claim 7 wherein said adjuster receiving portions are located more outside of said axes of said camshafts. 
     
     
       9. The cylinder head according to claim 8, further comprising an annular plug receiving portion concentric with said combusiton chamber. 
     
     
       10. The cylinder head according to claim 8 wherein said first supporting potions and said second supporting portions are arranged symmetrically about said plug receiving sleeve portion.